[PATCH RT 20/25][RFC 3.0.23-rt39-rc1] futex/rt: Fix possible lockup when taking pi_lock in proxy handler

[Steven Rostedt <rostedt@goodmis.org>]

[-- Attachment #1: 0020-futex-rt-Fix-possible-lockup-when-taking-pi_lock-in-.patch --]
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From: Steven Rostedt <rostedt@goodmis.org>

When taking the pi_lock, we must disable interrupts because the
pi_lock can also be taken in an interrupt handler.

Use raw_spin_lock_irq() instead of raw_spin_lock().

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Carsten Emde <C.Emde@osadl.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <clark.williams@gmail.com>
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190345.165160680@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/rtmutex.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 789744a..a02fbd9 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -1365,14 +1365,14 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
 	 * PI_REQUEUE_INPROGRESS, so that if the task is waking up
 	 * it will know that we are in the process of requeuing it.
 	 */
-	raw_spin_lock(&task->pi_lock);
+	raw_spin_lock_irq(&task->pi_lock);
 	if (task->pi_blocked_on) {
-		raw_spin_unlock(&task->pi_lock);
+		raw_spin_unlock_irq(&task->pi_lock);
 		raw_spin_unlock(&lock->wait_lock);
 		return -EAGAIN;
 	}
 	task->pi_blocked_on = PI_REQUEUE_INPROGRESS;
-	raw_spin_unlock(&task->pi_lock);
+	raw_spin_unlock_irq(&task->pi_lock);
 #endif
 
 	ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
-- 
1.7.8.3